In February, a petition to cancel the state visit got enough signatures to prompt a debate in Parliament. And that discussion was — colorful.

"It's extraordinary that Trump from cavernous depths of his scientific ignorance is prepared to challenge conclusions of 97 percent of the world's experts on this matter," said Paul Flynn, Labour Party Parliament member.

"There is something quite refreshing about a politician actually doing what they said they'd do before they were elected," said Adam Holloway, Conservative Party Parliament member.

Officials in both the U.K. and the U.S. have blasted Trump for what he said about Khan.

But the White House has defended the president's comments.

"I don't see that the president is picking a fight with the mayor of London at all," White House deputy press secretary Sarah Sanders told reporters.